Encapsulating compositions

ABSTRACT

An encapsulating composition for electronic devices comprises a curable material such as an epoxy resin and an ion scavenger compound selected from certain calixarene or oxycalixarene compounds in which at least half of the phenolic groups have been substituted by specific groups and certain silacrown compounds. Exemplary ion scavenger compounds include ##STR1## the tetraethyl acetate of 7, 13, 19, 25-tetra-tertbutyl-27, 28, 29, 30-tetrahydroxy-2,3-dihomo-3-oxacalix-4-arene and 1,1-dimethasila-17-crown-6.

This is a continuation of U.S. patent application Ser. No. 100,494,filed Sept. 24, 1987, now abandoned, which is a continuation-in-part ofU.S. patent application Ser. No. 870,677, filed Jun. 4, 1986, now U.S.Pat. No. 4,699,966, which is a continuation-in-part of U.S. patentapplication Ser. No. 717,251, filed Mar. 28, 1985, now U.S. Pat. No.4,642,362, which is a continuation-in-part of U.S. patent applicationSer. No. 673,621, filed Nov. 21, 1984, now U.S. Pat. No. 4,556,700. Thisis also a continuation-in-part of U.S. patent application Ser. No.088,945, filed Aug. 24, 1987, now allowed, which is acontinuation-in-part of U.S. patent application Ser. No. 914,491, filedOct. 2, 1986, now U.S. Pat. No. 4,718,966, which is a division of U.S.patent application Ser. No. 766,536, filed Sept. 16, 1985, now U.S. Pat.No. 4,636,539, which is a division of U.S. patent application Ser. No.673,621, filed Nov. 21, 1984, now U.S. Pat. No. 4,556,700.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to encapsulating compositions for electronicdevices such as semiconductor devices, integrated circuits andmicroelectronic components.

2. Description of the Related Art

Resin compositions, particularly based on silicone resins or epoxyresins, are well known for encapsulating electronic devices. It is alsowell known that such compositions are often contaminated by traceamounts of metal ions, particularly alkali metal ions. If such metalions are permitted to migrate in the composition, they can adverselyaffect the performance of the electronic device and may ultimately leadto device failure. Chloride ions can also give rise to a corrosionproblem.

It has been suggested to incorporate a crown ether or cryptate ether insuch compositions as metal ion scavengers (U.S. Pat. Nos. 4271425 and4278784 of Ching-Ping Wong, referring to Japanese Patent No. 76-11377 ofKaneda et. al.). However crown ethers and cryptate ethers are unsuitablefor commercial use because of their high toxicity.

U.S. Pat. No. 4556700 of S. Harris et. al. describes the use in adhesivecompositions of calixarene compounds represented by the formula ##STR2##where R¹ is alkyl, alkoxy, substituted alkyl or substituted alkoxy; R²is H or alkyl; and n'=4,6 or 8. It had previously been suggested to usecrown ethers as accelerators in these compositions.

McKervey et. al., J. Chem. Soc. Commun. 1985 p. 388 describes the cationtransfer properties of alkyl calixaryl acetates. These ester calixarenesare known to be capable of sequestering alkali metals. However thebehavior of calixarene derivatives in the environment of anencapsulating composition could not be predicted. The present inventorshave found that certain calixarene derivatives can scavenge alkali metalions so efficiently that an epoxy resin which would not normally beregarded as useful for electronic applications can be converted to amaterial having a relatively low level of contamination.

The same paper by McKervey et. al. compares the selectivity towardsalkali metal picrates of alkyl calixaryl acetates, 18-crown-6, and asilacrown. The results published in that paper suggest that thesilacrown is substantially less efficient for ion transport and has lowsodium sequestering ability, as compared to the calixarene derivativesand 18-crown-6. We have now unexpectedly found that silacrowns have alevel of activity comparable to 18-crown-6 and calixarene derivatives asalkali metal ion scavengers in encapsulating compositions. Thisillustrates the unpredictable nature of metal scavenging ability inencapsulating compositions. We have identified a range of compoundswhich are suitable as metal ion scavengers in such compositions.

SUMMARY OF THE INVENTION

The present invention provides an encapsulating composition forelectronic devices which comprises a polymeric material and a metal ionscavenger selected from

(A) Calixarene or oxacalixarene derivatives represented by the formula##STR3## wherein m'+m"=0-8;

n=0-8;

m'≧1/2(m'+m");

3≦m'+m"+n≦8;

if n=0, m'+m"≧4;

R³ is H, halogen, or hydrocarbyl, or a substituted derivative thereof,and R³ may be the same or different on each aryl group;

R⁴ is hydrocarbyl, hydrocarbyloxy or a substituted derivative thereof;or

R⁴ is ##STR4## wherein R⁵ and R⁶ which may be the same or different areH, or hydrocarbyl or a substituted derivative thereof;

R¹⁵ is H or hydrocarbyl or a substituted derivative thereof;

the calixarene or oxacalixarene derivative being present as a compoundper se or being bound into the polymer network of the polymericmaterial;

(B) Silacrowns represented by the formula ##STR5## wherein R⁷ and R⁸which may be the same or different are hydrocarbyl, hydrocarbyloxy, or anitrogen-substituted or other substituted derivative thereof; z is 3-6;and

(C) Polyalkylene ether glycols and ether derivatives thereof representedby the formula IV, V, VI or VII below:

    R.sup.9 --(R.sup.10 --O).sub.q --R.sup.11                  IV

wherein

q is an integer of from 2 to 3000;

R¹⁰ is a substituted or unsubstituted alkyl residue having 2 to 6 carbonatoms; the (R¹⁰ --O) groups containing the same alkyl residue orcontaining 2 or more different alkyl residues which may be distributedon the chain in a random or block manner;

R¹¹ is hydrogen, or hydrocarbyl or a substituted derivative thereof;

R⁹ is hydroxy, or hydrocarbyloxy or a substituted derivative thereof;##STR6## wherein R¹² is --(R¹⁰ --O)_(q) --R¹¹ in which R¹⁰, R¹¹ and qare as defined above; ##STR7## wherein R¹² is as defined above;

R¹³ is hydrogen, halogen, or hydrocarbyl or a substituted derivativethereof; and

x is an integer from 4 to 8; ##STR8##

wherein R¹⁰, R¹¹ and q are as defined above.

Exemplary of hydrocarbyl groups there may be given alkyl, alkenyl, aryland moieties having both non-aryl hydrocarbyl and aryl hydrocarbylportions. Exemplary of hydrocarbyloxy groups there may be given non-arylcontaining hydrocarbyloxy, aryloxy and oxy moieties having both non-arylhydrocarbyl and aryl hydrocarbyl portions.

The metal ion scavenger is added in an effective amount which maysuitably be from 0.5 to 10% by weight, based on the polymeric material.

A polymeric material having a calixarene derivative of formula II aboveincorporated into the polymer network is preferably of the kinddescribed in European patent application No. 0196895A2 which describes,inter alia, polyorganosiloxanes having at least one calixarene groupbound thereto. For example, a trialkoxysilyl calixarene derivative ofthe formula: ##STR9## may be used to crosslink polydimethylsiloxanediolin the presence of a tin salt so that it is incorporated into the curedRTV silicone network. A calixarene derivative bound into a polymernetwork has the advantage that it cannot leach out during the workinglife of the encapsulating composition.

In the above compounds of formula II-VII, the non-aryl hydrocarbyl orhydrocarbyloxy groups shall preferably contain from 1 to 10 carbonatoms, more preferably from 1 to 5 carbon atoms and the aromatichydrocarbyl and aromatic hydrocarbyloxy groups shall preferably havefrom 6 to 20 carbon atoms, more preferably from 6 to 10 carbon atoms.Non-aryl hydrocarbyl groups are preferred, especially alkyl or alkenylgroups. A substituted derivative of the foregoing may suitably besubstituted with one or more halo groups or substituted or interruptedby one or more oxo groups. Halogen may be chlorine, bromine, fluorine oriodine.

The preferred calixarene or oxacalixarene derivatives of formula II arethose in which m"=0.

The preparation of calixarene derivatives is known and is described, forexample, in C. Gutsche et. al. Acc. Chem. Res., 16, 161-170 (1983); inU.S. Pat. No. 4556700 Harris et al., and in J. Inclusion Phenomena 2199-206 (1984) D. Reidel Publishing Company.

The preparation of aryl calixarene derivatives including those offormula XIII, XIV, XV, XVI and XVII below is described in Europeanpatent application No. 87306963.7 and equivalent applications in othercountries. ##STR10##

Mixed functionality calixarene derivatives (i.e. wherein n=0 and m" 1)are described in European patent application No. 0196895A2 and U.S. Pat.No. 4642363 Harris et. al. When m" is greater than or equal to 2, thearyl groups having the --O--R¹⁵ side chain may be interspersed aroundthe ring between the aryl groups having the --OCH₂ C (O) R⁴ side chain.

In the oxacalixarene derivatives of formula II when (m'+m") and n aregreater than 2, the methyl and ether bridges may or may not alternatewithin the oxacalixarene molecule.

Preferred etherified oxacalixarenes of formula II are

(i) an oxacalix-4-arene of formula ##STR11##

(ii) a dioxacalix-4-arene of formula ##STR12##

(iii) a trioxcalix-3-arene of formula: ##STR13## wherein R¹⁶ is --CH₂C(O) R⁴, and R³ and R⁴ are as defined above.

Oxacalixarene compounds may be readily synthesised by methods describedin C. Gutsche et. al., J. AM. Chem. Soc. 103, 3782 (1981); B. Dhawan etal., J. Org. Chem., 48, 1536 (1983) and U.S. Pat. No. 4 098 717 Burikset al.

Etherified oxacalixarenes of formula II may be produced by reacting aphenolic oxacalixarene with a halomethyl acetone or a haloalkyl acetate.Potassium iodide may be added to accelerate etherification. This methodof production and the etherified oxacalixarenes of formula II are thesubject of Irish patent application No. 153/87 filed 21 Jan. 1987.

Amide-functional calixarenes and oxacalixarenes of formula II may beprepared by methods described in G. Calestani et al., J. Chem. Soc.,Chem. Commun., 1987, 344. The amide-functional oxacalixarene derivativesare novel compounds and are covered in an Irish patent application No.2574/87 entitled "Nitrogen-containing Oxacalixarenes and CalixareneDerivatives and use of such Compounds" filed 24 Sept. 1987.

Silacrowns of formula III are commercially available, e.g. from PetrarchSystems, Bristol, Pa., U.S.A. Suitable silacrowns and the preparationthereof are described in B. Arkles et al., "Silacrowns, a New Class ofImmobilizable Phase Transfer Catalysts", American Chemical SocietySymposium Series No. 192 - Chemically Modified Surfaces in Catalysis andElectrocatalysis, (Joel S. Miller, editor) 1982; and in Organometallics,Vol. 2, No. 3, 1983, 454. Suitable silacrowns include1,1-dimethylsila-11-crown-4, 1,1-dimethylsila-14-crown-5, and1,1-dimethylsila-17-crown-6.

Polyalkylene ether glycols and ether derivatives thereof arecommercially available or can be prepared by well known procedures. Inthe compounds of formula IV, V or VI, the value of q is preferably inthe range 2-25, more especially 3-6. Compounds of formula V and VI arecovered in our Irish patent application No. 204/87 filed 27 Jan. 1987.Calixarene derivatives of formula VI may be prepared by the processesdescribed in the literature already mentioned above. Cyclotriveratrylenecompounds of formula V may be synthesised as described in J. A. Hyatt,J. Org. Chem. 43 1808-1811 (1978), the contents of which areincorporated herein by reference.

Compounds of formula VII may be prepared as described in"Tris(polyoxaalkyl)amines (Tridents), a New Class of solid-liquidPhase-Transfer Catalysts", G. Soula, J. Org. Chem., Vol. 50, No. 20,1985, p. 3717.

The polymeric material may be any of the resins known for encapsulatingcompositions, particularly silicone resins such as RTV silicone resins,and epoxy resins, see for example U.S. Pat. Nos. 4 271 425 and 4 278 784and Japanese Pat. No. 76-11377.

The metal ion scavengers in the compositions of the present inventionhave a substantial advantage over crown ethers in commercial use becausethey are of low toxicity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is illustrated in the following Examples.

EXAMPLE 1.

To 32.4 g (0.049 mole) p-t-butylcalix-4-arene was added 60.0 g (0.435mole) pulverised anhydrous potassium carbonate, 33.2 g (0.200 mole)pulverised anhydrous potassium iodide and 80.0 g (0.865 mole)chloroacetone and 1.5 l dry analar acetone and the entire was refluxedfor 17 hr. under dry nitrogen with stirring. The cooled reaction mixturewas then added to 9 liters of water and the product precipitated as anoff-white solid. This solid was then washed well with 5% aqueous sodiumthiosulphate followed by water after which it was dissolved indichloromethane and this organic phase washed with 5% aqueous potassiumhydroxide, then water and then 5% aqueous hydrochloric acid, followed bywater. The organic phase was then dried over dried magnesium sulphateand the dichloromethane distilled off, the last traces at reducedpressure to give 35.3 g of off white powdered product. Tworecrystallisations from methoxyethanol afforded 18.0 g of colourlesscrystalline product m.pt. 201°-201.5° C. which was characterised by i.r.and elemental analysis as ##STR14##

EXAMPLE 2.

To 100 g of epoxy resin ERL 4221 Electronic Grade (E.G.) which iscommercially available from Union Carbide Corporation, Danbury, Conn.,U.S.A. and which is believed to be 3,4-epoxycyclohexyl methylcyclohexanecarboxylate, was added 1 g of the calixarene derivative ofExample 1. The composition was stirred well in a polyethylene beakerwith PTFE-coated stirrer for 17 hours to effect complete dissolution.

EXAMPLE 3.

A formulation of 100 g of epoxy resin Quatrex 1010 which is commerciallyavailable from The Dow Chemical Company, Midland, Mich., U.S.A. andwhich is believed to be diglycidyl ether of Bisphenol A (lowhydrolysable chloride level), and 1 g of the calixarene derivative ofExample 1 was prepared as above in Example 2.

EXAMPLE A (Comparative)

A formulation consisting of 100 g epoxy resin ERL 4221 EG and 1 g of18-crown-6 was prepared as in Example 2.

EXAMPLE B (Comparative)

A formulation consisting of 100 g epoxy Quatrex 1010 and 1 g of18-crown-6 was prepared as in Example 3.

EXAMPLE 4

To 10 g of the formulation of Example 2 was added 8 g of anhydrideAC-DP-1 (which is commercially available from Anhydrides and ChemicalsIncorporated, N.Y., U.S.A. and which is believed to be methyl tetrahydrophthalic anhydride) and the mixture was well stirred and then placed ina PTFE mould and cured for 15 minutes at 175° C. The cooled cured epoxywas then mechanically finely ground (100 mesh).

EXAMPLE C (Comparative)

To 10 g of the formulation of Example A was added 8 g of anhydrideAC-DP-1 and the same procedure followed as in Example 4.

EXAMPLE D (Comparative)

Example 4 was followed except that no additive was used with ERL 4221E.G.

EXAMPLE 5

To 10 g of the formulation of Example 3 was added 2.5 gpoly(oxypropylene) diamine (Commercially available under the Trade MarkJeffamine D-230 from Texaco Chemical Company, Bellaire, Tex., U.S.A.)and the composition was stirred well and then placed in a PTFE mould andcured for 15 minutes at 120° C. The cooled cured epoxy was thenmechanically finely ground (100 mesh).

EXAMPLE E (Comparative)

To 10 g of the formulation of Example B was added 2.5 g ofpoly(oxypropylene) diamine and the same procedure was followed as forExample 5.

EXAMPLE F (Comparative)

To 10 g of Quatrex 1010 without any additive was added 2.5 gpoly(oxypropylene)diamine and the procedure of Example 5 was followed.

TEST RESULTS--TABLE I

The ionic impurities in the products of Examples 4 and 5 and C, D, E,and F were measured following a procedure given in "Development ofMicroelectronic Adhesives to meet the new U.S. Military Hybrid AdhesiveSpecifications" MIL-A-87172 by D. M. Shenfield (AblestikLaboratories--Subsidiary of National Starch and Chemical Corporation,Gardena, Calif., U.S.A.) in "5th European Hybrid MicroelectronicsConference 1985 Stresa, Italy", page 428--"Ionic impurities". Thus 3grams of powdered samples of the products of Examples 4, 5 C, D, E and Fwere refluxed with 150 g of deionised water for 20 hours. The procedurewas carried out in triplicate and a blank was also prepared. Thesesamples of water were then analysed for sodium and potassium ion contentby atomic absorption and chloride ion content by titration. Thefollowing results (expressed in parts per million) were obtained:

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample  Additive   Epoxy        Na.sup.+                                                                           K.sup.+                                                                            Cl.sup.-                            ______________________________________                                        Example 4                                                                             1%         ERL          18   9    <1                                          Calixarene 4221                                                               derivative +anhydride                                                         of Example 1                                                                             AC-DP-1                                                    Example C                                                                             1%         ERL          17   8    <1                                          18-crown-6 4221                                                                          +anhydride                                                                    AC-DP-1                                                    Example D                                                                             0          ERL          45   10   <1                                                     4221                                                                          +anhydride                                                                    AC-DP-1                                                    Example 5                                                                             1%         Quatrex 1010 23   <5   <1                                          Calixarene +Jeffamine-D230                                                    derivative of                                                                 Example 1.                                                            Example E                                                                             1%         Quatrex 1010 22   5    <1                                          18-crown-16                                                                              +Jeffamine-D230                                            Example F                                                                             0          Quatrex 1010 38   <5   <1                                                     +Jeffamine-D230                                            ______________________________________                                    

As can be clearly seen, the calixarene derivative of Example 1 givessimilar performance to 18-crown-6 in reducing extractable sodium andpotassium from cured epoxy resin when used as a 1% level additive.

EXAMPLE G (Comparative)

To 100 g of epoxy resin diglycidyl ether of Bisphenol A (Epikote 828non-electronic epoxy resin commercially available from Shell ChemicalCompany--Batch G) was added 25 g of poly(oxypropylene) diamine(Jeffamine D-230) and the procedure of Example 5 was followed.

EXAMPLE 6

To 100 g Epikote 828 (Batch 5) was added 1 g of a calixarene derivativeof the formula: ##STR15## prepared as described in U.S. Pat. No.4,556,700 by S. Harris et al. The composition was stirred well at roomtemperature in a polyethylene beaker with PTFE-coated stirrer for 17hours to effect complete dissolution. To 10 g of the formulation wasadded 2.5 g of poly(oxypropylene)diamine and the same procedure wasfollowed as for Example 5.

EXAMPLE H (Comparative)

To 100 g Epikote 828 (Batch G) was added 1 g of 18-crown-6 and theformulation was stirred as in Example 6. To 10 g of the formulation wasadded 2.5 g of poly(oxypropylene)diamine and the same procedure wasfollowed as for Example 5.

TEST RESULTS--TABLE II

The ionic impurities in the products of Examples 6, G and H weremeasured following the MIL-A-87172 procedure described above to give thefollowing results:

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample   Additive    Epoxy     Na.sup.+                                                                            K.sup.+                                                                            Cl.sup.-                            ______________________________________                                        Example G                                                                              0           Epikote 828                                                                             240   16   9                                                        +                                                                             Jeffamine                                                                     D-230                                                    Example 6                                                                              1% Calixarene                                                                             Epikote 828                                                                             30    10   3                                            derivative  +                                                                             Jeffamine                                                                     D-230                                                    Example H                                                                              1% 18-crown-6                                                                             Epikote 828                                                                             50    15   6                                                        +                                                                             Jeffamine                                                                     D-230                                                    ______________________________________                                    

This indicates the potential of an ordinary non electronic epoxy productbeing converted into an epoxy for use in electronic encapsulation byaddition of a calixarene derivative.

Also the calixarene derivative is significantly better than 18-crown-6at reducing extractable Na⁺, K⁺ and Cl⁻.

EXAMPLE J (Comparative)

Example G was repeated using a different batch of Epikote 828 (Batch J).

EXAMPLE 7

Preparation: The tetraethyl acetate of7,13,19,25-tetra-tert-butyl-27,28,29,30-tetrahydroxy-2,3-dihomo-3-oxacalix-4-arene.##STR16##7,13,19,25-tetra-tert.butyl-27,28,29,30-tetrahydroxy-2,3-dihomo-3-oxacalix-4-arenewas prepared following the method of C. D. Gutsche, B. Dhawan, K. H.No., and R. Muthukrishnan, J. Am. Chem. Soc. 103 p 3782 1981 fromp-tert-butylphenol, paraformaldehyde and aqueous 5N potassium hydroxidein refluxing xylene. To 3.2 g of this compound (0.0047 mole) in 25 mlanalar acetone was added 6.6 g (0.031 mole) ethyl bromoacetate and 4.2 g(0.030 mole) anhydrous potassium carbonate and the entire was refluxedunder dry nitrogen with stirring for 120 hours. After this time allvolatiles were removed including the excess ethyl bromoacetate underreduced pressure to give a buff coloured solid which was dissolved in 20ml dichloromethane which was washed 3 times with 20 ml 10% aqueous H₂SO₄ and twice with 20 mls water. The separated dichloromethane layer wasthen dried over dried magnesium sulphate and volatiles were removed togive 4.0 g of product as a pale buff solid of yield 83%, which waschromatographed on acid-washed alumina and dichloromethane as eluent togive, following removal of volatiles, colourless solid tetraethylacetate of7,13,19,25-tetra-tert.butyl-27,28,29,30-tetrahydroxy-2,3-dihomo-3-oxacalix-4-arene,m.pt. 63°-64° C., characterised by infra-red spectroscopy and elementalanalysis.

I.R. Spectroscopy results: γ1765 (S) cm⁻¹ C=O.

Elemental analysis results (Calculated for C₁₆ H₈₂ O₁₃ : C=71.59,H=8.08, O=20.34; Found: C=71.45, H=7.87, O=20.20).

EXAMPLE 8

To 100 g of Epikote 828 epoxy resin (Batch J) was added 1 g of theoxacalixarene derivative of Example 7. The composition was stirred wellin a polyethylene beaker with PTFE-coated stirrer for 17 hours and thenthe same procedure as in Example 5 was followed.

EXAMPLE 9

Example 8 was followed except 5 g of the oxacalixarene derivative fromExample 7 was added instead of 1 g.

TEST RESULTS--TABLE III

The ionic impurities in the products of Examples 8 and 9 were measuredfollowing the MIL-A-87172 procedure described above. The followingresults were obtained:

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample  Additive          Epoxy    Na.sup.+                                                                           Cl.sup.-                              ______________________________________                                        Example G                                                                             0                 Epikote  270  5                                                               828 resin                                           Example 8                                                                             1% oxacalixarene derivative                                                                     Epikote  17   <5                                                              828 resin                                           Example 9                                                                             5% oxacalixarene derivative                                                                     Epikote  20   <5                                                              828 resin                                           ______________________________________                                    

As can be clearly seen from the above results, the oxacalixarenederivative is effective at reducing extractable sodium and chloride fromcured epoxy resin when used at the above indicated levels.

EXAMPLE K (Comparative)

Example G was repeated using a further batch of Epikote 828 (Batch K).

EXAMPLE 10

Preparation: Diethylamide of p-t-butylpseudocalixarene ##STR17## To 3.84g p-t-butylpseudocalixarene also called7,13,19,25-tetra-tert.butyl-27,28,29,30-tetrahydroxy-2,3-dihomo-3-oxacalix-4-areneprepared as in Example 7 (0.0056 mole) in 25 mls dry DMSO was added 4.50g (0.030 mole) 2-chloro-N,N-diethylacetamide, 2.6 g (0.022 mole)potassium bromide and 5.6 g (0.041 mole) anhydrous potassium carbonatewas stirred under nitrogen at room temperature for 72 hours after whichthe reaction mixture was poured into 3% sulphuric acid to give anoff-white precipitate which was washed well with water and dried to give5.8 g (90%) yield of off-white product. Chromatography through neutralalumina using dichloromethane as eluent gave off-white product m.pt.111°-114° C. characterised by infra red spectroscopy and elementalanalysis.

i.r. spectroscopy results: γ1652 cm-¹ (S) C=O.

Elemental Analysis results (Calc'd for C₆₉ H₁₀₂ N₄ O₉ C:73.24, H:9.09;Found C:73.15, H:8.77).

EXAMPLE 11

To 100 g Epikote 828 epoxy resin (Batch K) was added 1 g of the compoundof Example 10. The composition was then stirred well in a polyethylenebeaker with PTFE coated stirrer for 17 hours at room temperature, thenthe same procedure as in Example 5 was followed.

EXAMPLE 12

Example 11 was followed except that 5 g of amide-functionaloxacalixarene of Example 10 was used in place of 1 g.

TEST RESULTS--TABLE IV

The ionic impurities in the products of Examples 11 and 12 were measuredfollowing the MIL-A-87172 procedure described above. The followingresults were obtained.

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample   Additive      Epoxy    Na.sup.+                                                                           K.sup.+                                                                            Cl.sup.-                            ______________________________________                                        Example K                                                                              0             Epikote  37   <5   <4                                                         828 resin                                              Example 11                                                                             1% amide-functional                                                                         Epikote  20   <5   >2                                           oxacalixarene 828 resin                                                       derivative                                                           Example 12                                                                             5% amide-functional                                                                         Epikote  13   <5   <3                                           oxacalixarene 828 resin                                                       derivative                                                           ______________________________________                                    

As can be clearly seen the amide functional oxacalixarene is effectiveat reducing extractable sodium (and potassium and chloride) from curedepoxy resin when used at the above indicated levels. By employing 1%amide functional oxacalixarene, a non-electronic epoxy Epikote 828 hadits extractable metal ions reduced down to values expected from a goodelectronic epoxy resin.

EXAMPLE 13

To 100 g of Epikote 828 epoxy resin (Batch K) was added 1 g of ##STR18##m.pt. 230°-3° C. prepared following the procedure of G. Calestani J.Chem. Soc. Chem. Commun. 1987 p 344 (published m.pt. 228°-9° C.). Thecomposition was stirred well in a polyethylene beaker with PTFE coatedstirrer for 17 hours at room temperature, then the same procedure as inExample 5 was followed.

EXAMPLE 14

Example 13 was followed except that 5 g of the amide-functionalcalixarene was used in place of 1 g.

TEST RESULTS--TABLE V

The ionic impurities in the products of Examples K, 13 and 14 weremeasured following the MIL-A-87172 procedure described above.

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample   Additive      Epoxy    Na.sup.+                                                                           K.sup.+                                                                            Cl.sup.-                            ______________________________________                                        Example K                                                                              0             Epikote  37   <5   <4                                                         828 resin                                              Example 13                                                                             1% amide-functional                                                                         Epikote  5    <5   <2                                           calixarene derivative                                                                       828 resin                                              Example 14                                                                             5% amide-functional                                                                         Epikote  16   <5   <2                                           calixarene derivative                                                                       828 resin                                              ______________________________________                                    

As can be cleary seen the amide-functional calixarene is effective atreducing extractable sodium (and potassium and chloride) from curedepoxy resin when used at the above indicated levels. The result from useof 1% additive is encouraging, a non-electronic epoxy Epikote 828 havingits extractable metal ions reduced down to those of a good electronicepoxy.

EXAMPLE L (Comparative)

Example G was repeated using a further batch of Epikote 828 (Batch L).

EXAMPLE 15

To 100 g of Epikote 828 (Batch L) epoxy resin was added 1 g of1,1-dimethylsila-17-crown-6 commercially available from PetrarchSystems, Bristol, Pa., U.S.A. The composition was then stirred well in apolyethylene beaker with PTFE-coated stirrer for 10 minutes, then thesame procedure as in Example 5 was followed.

EXAMPLE 16

Example 15 was followed except that 5 g of 1,1-dimethylsila-17-crown-6was added instead of 1 g.

TEST RESULTS--TABLE VI

The ionic impurities in the products of Example L, 15 and 16 weremeasured following the MIL-A-87172 procedure described above.

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample   Additive  Epoxy     Na.sup.+                                                                            K.sup.+                                                                             Cl.sup.-                             ______________________________________                                        Example L                                                                              0         Epikote 828                                                                             120   5.5   5                                                       Resin                                                      Example 15                                                                             1% silacrown                                                                            Epikote 828                                                                             25    5     <3                                                      Resin                                                      Example 16                                                                             5% silacrown                                                                            Epikote 828                                                                             20    3     <3                                                      Resin                                                      ______________________________________                                    

As can be clearly seen from the above table the silacrown is effectiveat reducing extractable sodium, potassium and chloride from cured epoxyresin when used at the above indicated level.

As can be clearly seen by comparison of Table VI and Table II, theimprovements conferred by the silacrown are of the same order conferredby 18-crown-6 and the calixarene derivative of Example 6. The goodperformance conferred by the silacrown is completely unexpected due toits low sodium ion sequestering ability. (See M. A. McKervey et al J.Chem. Commun. 1985 p. 388). Silacrowns have the advantage of being muchless toxic than crown ethers.

EXAMPLE 19

To 100 g of Epikote 828 (Batch L) epoxy resin was added 5 g oftriethylene glycol monoethyl ether (98% purity, available from FlukaChemicals Ltd., Glossop, Derbyshire, England). The composition wasstirred well in a polyethylene beaker with PTFE-coated stirrer for tenminutes, then the same procedure as in Example 5 was followed.

TEST RESULTS--TABLE VII

The ionic impurities in the products of Examples L and 17 were measuredfollowing the MIL-A-87172 procedure described above. The followingresults were obtained:

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample                                                                              Additive         Epoxy    Na.sup.+                                                                           K.sup.+                                                                            Cl.sup.-                            ______________________________________                                        Ex-   0                Epikote  120  5.5  5                                   ample                  828 Resin                                              L                      (Shell)                                                Ex-   5%               Epikote  28   4    <3                                  ample HO(CH.sub.2 CH.sub.2 O).sub.3 CH.sub.2 CH.sub.3                                                828 Resin                                              17                     (Shell)                                                ______________________________________                                    

EXAMPLE M (Comparative)

Example G was repeated with a different batch of Epikote 828 epoxy resin(Batch M).

EXAMPLE 18

To 100 g of Epikote 828 (Batch M) epoxy resin was added 1%tris(3,6-dioxaheptyl)amine (an acylic cryptand having the formula##STR19## commercially available under the designation TDA-1 fromRhone-Poulenc, Courbevoie, France) with stirring for 10 minutes, thenthe same procedure as in Example 5 was followed.

EXAMPLE 19

The same procedure as in Example 18 was followed except that 5% TDA-1was employed instead of 1%.

EXAMPLE 20

Preparation Ethyl Ether of Triethyleneglycol of p-t-Butylcalix-8-arene##STR20## The tosylate of the ethyl ether of triethylene glycol wasprepared by reacting the alcohol with 1.1 equivalents of p tosyl in drypyridine as a pale yellow oil following the procedure of J. A. Hyatt, J.Org. Chem 43 (9) p. 1808 1978. To. 0.97 g (0.00075 mole) ofp-t-butylcalix-8-arene in 10 mls dry N-methyl pyrrolidone was added 2.65g (0.0080 mole) triethylene glycol monoethyl ether p-toluenesulphonateand the reaction mixture was stirred under nitrogen at room temperaturefor four hours. After this time 0.168 (0.0070 mole) sodium hydride wasadded to the reaction mixture and the entire was heated 17 hr at 90° C.under nitrogen with rapid stirring. After cooling to room temperatureN-methyl pyrrolidone was distilled off under reduced pressure to give abrown sticky solid residue. To this residue was added 20 mlsdichloromethane and solid was filtered off to give a clear red brownfiltrate which was washed three times with 20 mls 10% aqueous H₂ SO₄ andonce with water following which it was dried over MgSO₄. Followingsolvent removal 1.40 g pale red-brown oil product remained (70%) whichon standing partly solidified. The product was chromatographed onacid-washed alumina using dichloromethane as eluent to give pale yellowbrown oil which again partly solidified on standing. Infra redspectroscopy revealed it to be the monoethyl ether of triethyleneglycolof p-t-butylcalix-8-arene.

i.r. spectroscopy results:γ1120 cm⁻¹ (S)C-O-C (No 3320cm⁻¹ due to C-OH).

This compound and other calixarene polyalkylene glycol derivatives canalso be prepared by reaction of phenolic calixarene with epoxide (U.S.Pat. No. 4098717 Jul. 4 1978 by R. Buriks et al, Petrolite Corp.).

EXAMPLE 21

A 1% level of calixarene from Example 20 was added to Epikote 828 (BatchN) resin with stirring as in Example 19 but for 17 hours to ensurecomplete dissolution and the composition was then treated as in Example5.

EXAMPLE 24

Example 23 was followed except that a 5% level of calixarene derivativefrom Example 22 was used in place of 1%.

TEST RESULTS--TABLE VIII

The ionic impurities in Example M, 18, 19, 21 and 22 were measuredfollowing the MIL-A-87172 procedure as described above.

The following results were obtained:

    ______________________________________                                        Analysis of Aqueous Samples (p.p.m.)                                          Sample   Additive    Epoxy    Na.sup.+                                                                            K.sup.+                                                                            Cl.sup.-                             ______________________________________                                        Example M                                                                              0           Epikote  270   7    5                                                         828 Resin                                                Example 18                                                                             1% TDA-1    Epikote  20    4.5  --                                                        828 Resin                                                Example 19                                                                             5% TDA-1    Epikote  3-5   2    <3                                                        828 Resin                                                Example 21                                                                             1% Calixarene                                                                             Epikote  17    <3                                                 dervivative 828 Resin                                                Example 22                                                                             5% Calixarene                                                                             Epikote  10    5.5  <3                                            derivative  828 Resin                                                ______________________________________                                    

As can be clearly seen the polyethylene derivatives are effective atreducing extractable sodium (and potassium and chloride) from curedepoxy resin when used at the above indicated levels.

We claim:
 1. An improved curable composition suitable for theencapsulation of electronic devices, said composition comprising acurable epoxy resin and, as the improvement therefor, from 0.5 to 10percent by weight of a metal ion scavenger effective in reducing thelevel of metal ion or chloride ion or both metal ion and chloride ionextractables from said composition, said metal ion scavenger selectedfrom the group consisting of(A) Calixarene or oxacalixarene derivativesrepresented by the formula ##STR21## wherein m'+m"=0-8;n=0-8;m'≧1/2(m'+m"); ≦ m'+m"+n≦8; if n=0, m'+m"≧4; the R³ groups are the sameor different and are H, halogen, or hydrocarbyl or a substitutedderivative thereof; R⁴ is hydrocarbyl, hydrocarbyloxy or a substitutedderivative thereof; or R⁴ is ##STR22## wherein R⁵ and R⁶ are the same ordifferent and are H or hydrocarbyl or a substituted derivative thereof;R¹⁵ is H or hydrocarbyl or a substituted derivative thereof; thecalixarene or oxacalixarene derivative being present as a compound perse or being bound into the polymer network of the polymeric material;(B) Silacrowns represented by the formula ##STR23## wherein R⁷ and R⁸are the same or different and are hydrocarbyl, hydrocarbyloxy, or anitrogen-substituted or other substituted derivative thereof; z is 3-6;and (C) polyalkylene ether derivatives represented by the formulae##STR24## wherein R¹² is --(R¹⁰ --O)_(q) --R¹¹ ;q is an integer of from2 to 25; R¹⁰ is a substituted or unsubstituted alkyl residue having 2 to6 carbon atoms, the (R¹⁰ --O) groups containing the same alkyl residueor containing different alkyl residues distributed on the chain in arandom or block manner; R¹¹ is hydrogen, hydrocarbyl or a substitutedderivative thereof; R¹³ is hydrogen, halogen, or hydrocarbyl or asubstituted derivative thereof; and x is an integer from 4 to
 8. 2. Acomposition according to claim 1 wherein the metal ion scavenger is acompound of formula II wherein m"=0.
 3. A composition according to claim1 wherein the metal ion scavenger is a calixarene derivative of formulaII wherein n=0.
 4. A composition according to claim 1 wherein the metalion scavenger is an oxacalixarene derivative of formula II wherein n isfrom 1 to
 4. 5. A composition according to claim 3 wherein theoxacalixarene of formula II is selected from the group consisting of(i)an oxacalix-4-arene of formula ##STR25## (ii) a dioxacalix-4-arene offormula ##STR26## (iii) a trioxacalix-3-arene of formula ##STR27##wherein R¹⁶ is CH₂ C(O) R⁴ ;R³ is H, halogen, or hydrocarbyl or asubstituted derivative thereof, and R³ may be the same or different oneach aryl group; and R⁴ is hydrocarbyl, hydrocarbyloxy or a substitutedderivative thereof; or R⁴ is ##STR28## wherein R⁵ and R⁶ which may bethe same or different are H or hydrocarbyl or a substituted derivativethereof.
 6. A composition according to claim 1 wherein the metal ionscavenger is a silacrown selected from the group consistingof1,1-dimethylsila-11-crown-4, 1,1-dimethylsila-14-crown-5, and1,1-dimethylsila-17-crown-6.
 7. A composition according to claim 1wherein the metal ion scavenger is a compound of formula V or VI inwhich q is an integer from 2 to
 6. 8. A composition according to claim 1wherein the metal ion scavenger is present in an amount of from 1 to 5%by weight based on the weight of the polymeric material.
 9. An improvedcurable composition suitable for the encapsulation of electronicdevices, said composition comprising a epoxy resin and, as theimprovement therein, an effective metal or chloride ion scavengingamount of a calixarene derivative represented by the formula: ##STR29##wherein R¹⁴ is H, hydrocarbyl or a substituted derivative thereof, R¹⁵is hydrocarbyl, hydrocarbyloxy or a substituted derivative thereof; andr is 4, 6 or
 8. 10. A composition according to claim 1 wherein thehydrocarbyl group of R³, R⁴, R⁵, R⁶, R⁷, R⁸, R¹¹ or R¹⁵ and thehydrocarbyloxy group of R⁴, R⁷ or R⁸ contains from 1 to 10 carbon atomsif non-aryl containing and from 6 to 20 carbon atoms if aryl or arylcontaining.
 11. A composition according to claim 10 wherein thehydrocarbyl group is an alkyl or alkenyl group.